1. Field of the Invention
The present invention generally relates to multi-piece golf balls and more particularly to golf balls having at least one component made of a composition comprising an oriented nanostructure. The multi-piece golf ball includes a core, which may be constructed of a center and surrounding outer core layer. Preferably at least one of the core layers is formed from a composition comprising a rubber material and the oriented nano structure. The golf ball further includes a cover, which may be a dual-cover having inner and outer cover layers.
2. Brief Review of the Related Art
Today, both professional and amateur golfers use multi-piece solid golf balls. Basically, a two-piece solid golf ball includes a solid inner core protected by an outer cover. The inner core is made commonly of a rubber material such as natural and synthetic rubbers: styrene butadiene, polybutadiene, or polyisoprene. Highly neutralized ethylene acid copolymer ionomer resins (HNPs) also may be used to form the core. The outer cover is made commonly of thermoplastic or thermoset resins such as ionomers, polyolefins, polyamides, polyesters, polyurethanes, and polyureas. As new materials and manufacturing processes have become more economically feasible, three-piece, four-piece, and five-piece solid golf balls have been introduced. Different materials are used in the golf ball construction to impart specific properties and playing features to the ball.
For example, the resiliency and rebounding performance of a golf ball is based primarily on its core. Balls having a high resiliency tend to reach a high velocity when struck by a golf club. As a result, the ball tends to travel a greater distance. This helps the ball travel longer distances. In a majority of golf balls used today, conventional cores comprise polybutadiene rubber (“PBR”). The core construction may be single or multi-layered. That is, the golf ball may include a single core layer (center). In another version, the golf ball may have a dual-core construction comprising an inner core and at least one surrounding core layer. In yet another version, the golf ball may contain a multi-layered core comprising an inner core, intermediate core layer, and outer core layer. The PBR compositions typically contain “fillers,” which are added to adjust the density and/or specific gravity of the material. Adjusting the weight of the golf ball either towards the center or outer surface of the ball changes the flight and spin characteristics of the ball.
The industry continues to look at new materials, for example, nano-sized materials such as nanofibers, nanotubes, and nanoparticles that could be used in constructing golf ball components. Kim et al., U.S. Pat. No. 6,794,447 discloses golf balls incorporating nanofiller material in their cores, outer cover layers, or, intermediate layers. The material includes a polymer such as polyamide, ionomer, polycarbonate, polyurethane, polystyrene, polyethylene, fluoropolymer, polyamide elastomer, thermoplastic polyolefin, polyester elastomer, polyester, polyolefin, thermoplastic elastomer, thermoplastic vulcanizate, or epoxy resin. Nano-particles of inorganic material are dispersed in the polymeric material. The particles have a size of one micron (μm) or smaller and particles preferably consist essentially of clay, such as hydrotalcite, montmorillonite, micafluoride, or octosilicate.
Jordan et al., US Patent Application Publication US 2007/0191526 discloses golf balls having a core and cover surrounding the core. At lest one of the layers is formed from a composition comprising nano-clays and a fully neutralized ethylene acid copolymer or other ionomer resin. The acid groups in the ionomer resin may be neutralized by a salt of an organic acid, a cation source, or a suitable base. The nano-clays are described as being high aspect ratio additives typically based on montmorillonite clay. The nano-clays preferably have a 50% average dry particle size of 6 μm or less and a 10% average dry particle size of 2 μm or less with a preferred aspect ratio of 100 to 150.
Sullivan et al., U.S. Pat. No. 7,261,647 discloses golf balls having a core, vapor barrier layer, and cover. The barrier layer is formed from a polymer comprising a nano-material s such as smectite minerals; carbon nanotubes; fullerenes; single-wall and multi-wall carbon nanotubes; polymer nanofibers; and carbon nanofibrils with an average particle size of less than 100 nm. According to Sullivan '647, the nano-material creates a tortuous path across the barrier layer to prevent vapor from penetrating therein. Suitable polymers are described as including ionomeric copolymers and terpolymers, thermoplastic elastomers, polybutadiene rubber, balata, grafted metallocene-catalyzed polymers, polyurethanes, and polyureas.
Isogawa et al., U.S. Pat. No. 7,294,069 discloses a golf ball having a core and cover layer. The resin composition used to form the cover layer contains a base resin and cation-treated phillosilicate in the form of nano-sized fine particles. The primary particles have a thickness of 10 nm or smaller, and are in the shape of flat plates having a length and a width of 1 nm or smaller. The '069 patent describes polyurethanes, ionomers, polyamides, polyesters, polyolefins, polystyrene-based elastomers, and mixtures thereof as being suitable base resins.
One drawback with adding nanostructures is that such fillers are generally difficult to disperse in the composition. The very small size of the particles makes them hard to disperse. As a result, agglomerates of particles may faun in the polymeric matrix. If a significant amount of agglomerates and aggregates form, they may negatively affect physical properties such as modulus and hardness. Because of this poor dispersibility, the desired levels of hardness and modulus may not be achieved when using such nanostructures.
It would be desirable to have a rubber composition containing nanostructures that could be used to make a core for a golf ball, wherein the nanostructures are dispersed highly throughout the composition. The nanostructures, for example, particles, tubes, or fibers, should be dispersed homogenously to prevent or minimize the tendency of particles to stick together and form aggregates. Also, good dispersion is important, because it means the material can be molded more easily into a golf ball core or other ball component.
The present invention provides golf ball cores and other ball components made from rubber compositions containing nanostructures. The nanostructures are homogenously dispersed in the rubber compositions, thus providing the material with good physical properties. In turn, the rubber compositions can be molded into components for golf balls. The resulting golf ball has high quality playing performance.